Method of fabricating a photosensitive structure

ABSTRACT

A method of fabrication of a photosensitive device is disclosed. A substrate with at least an insulator layer formed thereon is provided. The insulator layer comprises a plurality of photoreceiving regions, and a plurality of conductive patterns are formed thereon without covering the photoreceiving regions. A dielectric layer is formed on the insulator and the conductive patterns, and polished by CMP thereof. The dielectric layer comprises a first dielectric layer formed by PECVD and a second dielectric layer formed by HDPCVD.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a semiconductor device fabrication, andmore particularly to a method for forming a photosensitive device withcolor filter.

2. Description of the Related Art

FIG. 1 are schematic representations of structures in the final stagesof formation of a photosensitive device using conventional technology.Referring to FIG. 1A, a planarized inter-metal dielectric layer 100 witha photoreceiving region 130 therein is formed on a substrate (notshown). A metal layer 114 is deposited and defined to expose thephotoreceiving region 130 on the inter-metal dielectric layer 100, and aprotective layer 150 is formed thereon.

Referring to FIG. 1B, a thick planar film 152, for example spin-onglass, is coated on a protective layer 150 for planarization. The planarfilm 152 and protective layer 150 are transparent for enhancing lightsensitivity of the photosensitive device. A color filter process,comprising coating R, G, and B filters, development, etching and topcoating, is then performed to form color filter 112. Next, anotherprotective layer 120 is coated thereon to cover the color filter 112 andplanar film 152.

The coated planar film 152 described cannot effectively fill in someconcave areas of the photosensitive device to produce a flat surfaceover the entire wafer surface. Additionally, the planar film 152 mustachieve a thick thickness, about 2 μm, to produce a flat surface.Shrinkage, however, may be generated, affecting flatness of the surfaceof the planar layer 152. The uneven layer 152 under the color filter 112may diminish color performance of the device. Due to the unevenly coateddielectric layer 152, a yellow strip may occur in the step heightregions, for example the regions near the bonding pads or the scribelines.

SUMMARY OF THE INVENTION

Embodiments of the invention achieve technical advantages by providing achemical mechanical polishing (CMP) process in the fabrication of aphotosensitive device.

In accordance with an embodiment of the invention, a method forfabricating a photosensitive device comprises the following steps. Asubstrate with at least an insulator layer formed thereon is provided.The insulator layer comprises a plurality of photoreceiving regions, anda plurality of conductive patterns are formed thereon without coveringthe photoreceiving regions. A dielectric layer is formed on theinsulator and the conductive patterns, and polished by CMP thereof.

In accordance with an embodiment of the invention, a photosensitivedevice comprises the following elements, at least an insulator layercomprising a plurality of photoreceiving regions is disposed on asubstrate, a plurality of conductive patterns are disposed on theinsulator layer without covering the photoreceiving regions, adielectric layer with a flat surface is disposed on the conductivepatterns and the insulator layer, wherein the dielectric layer has athickness of 2000 Å˜4000 Å on the conductive patterns.

Further scope of the applicability of the present invention will becomeapparent from the detailed description given hereinafter. However, itshould be understood that the detailed description and specificexamples, while indicating preferred embodiments of the invention, aregiven by way of illustration only, since various changes andmodifications within the spirit and scope of the invention will becomeapparent to those skilled in the art from this detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will become more fully understood from thesubsequent detailed description and the accompanying drawings, which aregiven by way of illustration only, and thus are not limitative of thepresent invention, and wherein:

FIGS. 1A to 1B are schematic representations of structures in the finalstages during the formation of the photosensitive device usingconventional technology;

FIGS. 2A to 2D illustrate the fabrication method of a photosensitivedevice of an embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

FIGS. 2A to 2D illustrate the fabrication method of a photosensitivedevice of an embodiment of the invention. Referring to FIG. 2A, asubstrate, useful in forming a layered semiconductor device, is shownwherein an insulator layer 200 thereof comprises a photoreceiving region202. This insulator layer 200 is the final inter-metal dielectric layerformed in photosensitive device. The photoreceiving region 202 is alight-receiving region and will have a converter (not shown in thefigures) to transfer light into current. Hence, the material of thisinsulator layer 200 is transparent and can be made from any typical andwell-known dielectric material used in sensor device, but is preferablysilicon oxide.

A conductive layer (not shown) is deposited on the partially fabricateddevice. The material of this layer can be A1 and formed using any knowntechnique such as reactive sputtering process (with or withoutcollimation) wherein sputtering is carried out in an Ar+N2 atmosphereusing an A1 target. The thickness of this conductive layer can be in therange of about 8000 Å to about 10000 Å. The conductive layer ispatterned to expose the described photoreceiving region 202. Thepatterned conductive layer refers to conductive patterns 204 describedlater in this specification. The conductive patterns 204 can compriseconductive lines in cell regions, bonding pads or test pads with largestep height in the periphery regions or scribe lines.

Referring to FIG. 2B, a dielectric layer 206 is formed on the insulatorlayer 200 and the conductive patterns 204. In this embodiment, thedielectric layer 206 is formed of transparent materials, for examplesilicon oxide or silicon oxynitride, thus the device is photosensitive.The dielectric layer 206 can be deposited by any deposition method, suchas chemical vapor deposition (CVD), plasma enhanced chemical vapordeposition (PECVD), or high density plasma enhanced chemical vapordeposition (HDP). Preferably, the dielectric layer 206 comprises a firstdielectric layer deposited by HDP to 1000 Å˜2000 Å and a seconddielectric layer deposited by PECVD to 7000 Å˜10000 Å, thus increasingthe gap filling. The thickness of the deposited dielectric layer 206depends on the step height of the underlying conductive patterns 204, inwhich a gap between two conductive patterns 204 must be filled. Thedielectric layer 206 formed of silicon oxide can further comprise asilicon nitride layer deposited thereon to protect the underlyingphotosensitive device.

Referring to FIG. 2C, the dielectric layer 206 is polished to have auniformly flat surface 208 over the entire wafer surface. In a preferredembodiment, the dielectric layer 206 is polished by chemical mechanicalpolishing (CMP). Dielectric layer 206, formed of silicon oxide, can bepolished using fumed silica as slurry. In addition, the dielectric layer206 comprising a silicon nitride layer thereon, colloidal silica can beused as slurry during polishing. The polished dielectric layer 206preferably has a flat surface higher than the conductive pattern in arange between 2000 Å to 4000 Å.

Referring to FIG. 2D, a color filter process is performed using photoresist to form R, G and B color filter layers (210R, 210G and 210B)respectively, and a upper planar layer 212 is coated thereon. A microlens 214 is formed on the upper planar layer 212 by coating and definingan organic thin film, and a protective layer 216 is formed thereon.

FIG. 2D illustrates a photosensitive device of the embodiment. As shownin FIG. 2D, an insulator layer 200 comprising a plurality ofphotoreceiving regions 202 is formed on a substrate (not shown). Aplurality of conductive patterns 204 is disposed on the insulator layer200 without covering the photoreceiving regions 202. A dielectric layer206 with a flat surface is disposed on the insulator layer 200 and theconductive patterns 204, and surface of the dielectric layer 206 ishigher than the conductive patterns 204 in the range between 2000 Å to4000 Å. The dielectric layer 206 is formed of transparent materials,such as silicon oxide or silicon oxynitride, thus the device isphotosensitive. A color filter layer 210, an upper dielectric layer 212,a micro lens 214, and a protective layer 216 are disposed on thedielectric layer 206 in order.

Consequently, the dielectric layer 206 planarized by CMP is flatter thanthe planar layer formed by a conventional coating method. Specifically,due to the flat dielectric layer 206 achieved by CMP, yellow stripsoccurring in the conventional technology are ameliorated. Further, sincethe dielectric layer is planarized by CMP instead of coating a verythick film, better sensitivity and transmittance of photosensitivedevices can be achieved.

While the invention has been described by way of example and in terms ofthe preferred embodiments, it is to be understood that the invention isnot limited to the disclosed embodiments. To the contrary, it isintended to cover various modifications and similar arrangements (aswould be apparent to those skilled in the art). Therefore, the scope ofthee appended claims should be accorded the broadest interpretation soas to encompass all such modifications and similar arrangements.

1. A method for fabricating a photosensitive device, comprising thesteps of: providing a substrate with at least an insulator layer formedthereon, wherein the insulator layer comprises a plurality ofphotoreceiving regions therein, a plurality of conductive patterns areformed on the insulator layer without covering the photoreceivingregions; forming a dielectric layer on the insulator and the conductivepatterns; and polishing the dielectric layer, wherein the dielectriclayer comprises a first dielectric layer formed by PECVD and a seconddielectric layer formed by HDPCVD.
 2. The method as claimed in claim 1,wherein the dielectric layer is silicon oxide or silicon oxynitride. 3.The method as claimed in claim 1, wherein polishing of the dielectriclayer is accomplished by CMP.
 4. The method as claimed in claim 1,wherein the conductive patterns have a thickness of 8000 Å˜10000 Å. 5.The method as claimed in claim 1, wherein the polished dielectric layerhas a thickness of 2000 Å˜4000 Å A on the conductive patterns.
 6. Themethod as claimed in claim 1, further comprising forming a color filterlayer on the dielectric layer, coating an upper dielectric layer on thecolor filter layer, forming a plurality of microlenses on the upperdielectric layer, and forming a protective layer on the microlenses.